The present invention relates to a reviewing apparatus for reviewing samples under various review conditions, based on recipes in which the review conditions are registered. Especially, the invention relates to an apparatus that needs to optimize optical conditions because optimal optical conditions are different according to the characteristics of samples such as a SEM (scanning electron microscope)-based defect reviewing apparatus or SEM-based defect review tool. Furthermore, the invention relates to a reviewing apparatus that needs to optimize conditions for achieving both high capture rate and high throughput such as an automatic defect review (ADR) tool.
In semiconductor fabrication, it is important that defects produced during fabrication processes be discovered at early stages and countermeasures against them be taken, in order to secure high production yield. In recent years, as semiconductor devices have diminished in size, effects of even quite small defects on the yield can no longer be neglected. Defects to be reviewed have become more versatile.
A SEM-based defect reviewing apparatus is a tool for reviewing such various defects. Generally, this reviewing apparatus is used to review defects, based on defect locations detected by a host inspection tool. Where a manual review is performed, the sample stage is moved into coordinates outputted by the host inspection tool. Then, the sample is imaged at a low magnification at which the sample comes within the field of view. The position of the defect is checked visually. Then, the sample stage is moved such that the position of the defect comes to the center of the field of view. An image of the defect for review is acquired at high magnification. Automation of this sequence of process steps is ADR.
In ADR, various conditions including optical conditions corresponding to a sample, ADR mode, conditions under which low-magnification images are acquired, and conditions under which high-magnification images are acquired need to be optimized to achieve both high capture rate and high throughput. Because the number of combinations of items to be set is exorbitant, the ADR is a work which is difficult to optimize even for experienced skilled persons and which needs trial-and-error attempts. Therefore, there is a need for facilitation of the work for optimizing the contents of the settings.
A recipe setting method implemented in a defect inspection tool and consisting of setting a plurality of inspection conditions, effecting inspections under each condition, and adopting a condition under which the most defects can be detected as a final recipe setting is disclosed in patent reference 1 (JP-A-2005-017159).
A method of enabling recipe parameters setting forth fabrication processes in semiconductor fabrication equipment to be edited in a batch is disclosed in patent reference 2 (JP-A-05-283308).
Although the method disclosed in the above-cited patent reference 1 makes it possible to efficiently make trial-and-error attempts for recipe condition optimization, trial-and-error attempts are still made under varied conditions. Therefore, there is the problem that the processing time is long. When the conditions are varied, it is difficult for a novice to precisely judge how the conditions should be varied. Furthermore, in the case of a SEM-based defect-reviewing apparatus, the same sample is reviewed repeatedly, creating the possibility that damages to the sample are accumulated. Consequently, it is desired to avoid acquiring images repeatedly while varying review conditions.
The method disclosed in the above-cited patent reference 2 enables recipe parameters used in semiconductor fabrication equipment to be edited in a batch. This is effective in improving the efficiency of the intended editing work and reducing setting errors. However, there is no mention of any detailed method of analysis permitting one to judge as to how the set conditions should be varied to produce optimum results. In addition, when a new recipe is created, there is no mention of any detailed method of effectively exploiting the results of analysis of existing recipes.
It is a main object of the present invention to provide recipe analysis method, recipe setting method, and reviewing apparatus which permit even a novice to analyze the contents of existing recipe settings without trial-and-error attempts in the reviewing apparatus and to create a new recipe in a short time based on the result of the analysis.
To achieve the above-described object, an embodiment of the present invention provides a reviewing apparatus having a function of reviewing a sample under registered review conditions, based on a recipe in which the review conditions are registered. A main feature is to enable the contents of settings of plural set items for plural recipes to be displayed in the form of a list. Another main feature is to create a new recipe based on the results of analysis of common features, using the contents of settings having high degrees of commonality as initial settings.
According to the present invention, even a novice can analyze the contents of existing recipe settings. Especially, he can easily judge the commonality. Therefore, it is only required to examine the contents of settings regarding only items having low degrees of commonality. Hence, a novel recipe can be created in a short time. Furthermore, the throughput of the created recipe can be forecasted. Therefore, the validity of the set items can be confirmed. Where the contents of the settings are modified, the recipe settings can be optimized while checking the effects of the modification.
Embodiments of the present invention are described.
As the magnification of a low-magnification image becomes higher, defects are detected more easily. However, the probability that defects do not come within the field of view is increased. Consequently, optimization must be done taking account of the tradeoff between the size of the defect to be detected and the coordinate accuracy. In a first set of autofocus conditions for low-magnification images, a standard algorithm is used (Standard). In a second set of autofocus conditions, the processing speed is high but the accuracy is lower than that provided by the standard algorithm (Fast). In a third set of autofocus conditions, the processing speed is low but the accuracy is higher than that provided by the standard algorithm (Slow). As the number of added frames of low-magnification images is increased, noise is reduced. Therefore, where emphasis is placed on the capture rate rather than the throughput, the number of added frames of low-magnification images is set to a large value. The magnification of high-magnification images is determined according to the size of the defect to be reviewed. The magnification of high-magnification images, autofocus conditions for high-magnification images, and the number of added frames are similar in meaning to the magnification of low-magnification images, autofocus conditions, and the number of added frames, respectively, but are used for final check of the defect image. Therefore, settings are often made while placing emphasis on the image quality rather than the throughput in comparison with low-magnification images. Contents of settings including device name and automatic device classification (ADC) (not shown in
A procedure for analyzing the commonality among the set items is described taking the example of
With respect to the commonality among the set items, when the items of various contents of settings set for individual recipes contain items (herein referred to as common items) common to different recipes and the number of the common items is large in number, it is determined that the level of commonality is high. On the other hand, when the common items are few in number, it is determined that the level of commonality is low.
First, “Item” 402 to be analyzed for its commonality is selected using a pointing device such as a computer mouse. In this example, “Process” is selected. After “Item” has been selected, a keyword is entered using the input device such as a keyboard. A Search button 404 is depressed. In the illustrated example, a character string starting with A is specified as the keyword. Therefore, a recipe 405 having a Process name starting with A is displayed in the list display area 401. In this example, recipes displayed in the list are restricted using a Search function. Where recipes are few in number, it is not always necessary to limit recipes displayed. Furthermore, the list can be sorted by the Item to be analyzed.
Similarly, analysis of common terms of recipes 410, each having a “Process” name starting with B, reveals that the degree of commonality between High AF (411) of B3 and “High Frame” (412) of B2 is low. The result of the analysis shows that if the autofocus settings of the high-magnification image of B3 are set to a high-speed mode in the same way as B1 and B2, the throughput may be improved, and that if the number of added frames of high-magnification images of B2 is set to the same value as that of B1 and B3, an image of higher quality will be acquired. This would result in favorable results.
Where the settings are modified, an element of the list that the user wants to change is selected using the pointing device such as a mouse, and then the settings can be varied using the input device such as a keyboard. Plural elements may be selected and the settings may be modified in a batch mode.
A procedure of creating a recipe is now described. In this procedure, the contents of settings having high degrees of commonality are taken as initial values, based on the results of an analysis. As an example, a recipe 410 having a “Process name” starting with B is a subject to be analyzed. When the Analyze button 408 is depressed and the analysis is started, items having high degrees of commonality are displayed in the common item display area 413. In the present example, “Process:B*”, “ADR Mode:Cell”, “Low Mag:20k”, “Low AF:Fast”, “Low Frame:4”, “High Mag:60k”, “High AF:Narrow”, “High Frame:12” are shown initially. Where the contents of the settings are updated according to the need and a recipe having a “Process” name of B4, for example, is newly created, the “Process” name of “B*” is updated to “B4”. The recipe can be easily created by depressing “Save as” button 414.
The present invention can have the following configurations:
(1) A reviewing apparatus for acquiring review images of a sample, the reviewing apparatus comprising:
a storage device in which plural recipes are stored, the recipes having plural review conditions under which the review images are acquired, the review conditions being registered in the recipes;
an arithmetic unit for extracting common review conditions registered in all of the plural recipes from the first-mentioned review conditions, taking the common review conditions most frequently registered out of the common review conditions as initial review conditions, storing the initial review conditions in the storage device, and creating a new recipe under the initial review conditions; and
a display device for displaying information sent from the arithmetic unit;
wherein the arithmetic unit displays the plural recipes on one display screen of the display device in such a way that the common review conditions are distinguished from other conditions.
(2) A method of setting recipes for a reviewing apparatus for acquiring review images of a sample, said method comprising the steps of:
preparing plural recipes in which plural review conditions under which the review images are acquired are registered;
extracting common review conditions registered in all of the recipes from the recipes;
taking common review conditions most frequently registered out of the first-mentioned common review conditions as initial review conditions;
storing the initial review conditions in memory;
creating a new recipe using the initial review conditions;
causing the new recipe created using the initial review conditions to be displayed on a display device; and
displaying the plural recipes on one display screen of the display device in such a way that the common review conditions are distinguished from other conditions.
It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the spirit of the invention and the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-193479 | Jul 2007 | JP | national |